Caller-ID issue

[bbrown3730]

hello;
A user has forwarded calls from his desk phone to his cellular. These calls are all internal numbers for example 212-xxx-xxxx. However, some calls show up on his cell phone as the example above. However, some calls show up as +1212-xxx-xxxx. Does anyone know why the plus one appears?
Thanks.

 

[kyle555]

Carrier level stuff I`d reckon. If your PRI/SIP and the cell are all with carrier A, I'd say ask them!

If your PRIs are with Carrier A and buddy's cell is a number he ported from Carrier B to Carrier C, when a call is forwarded to the cell, Carrier A has to figure out how to route it.

I don't know about the US, but porting checks can be done at any level in the call flow.

Maybe carrier A, from their CO closest to you, looks up if that cell is ported. If so, it learns it needs to send the call to carrier C.
Maybe carrier A does that lookup a little further upstream in their PSTN
Maybe carrier A doesn't do a porting lookup at all for calls dialed from their network and they just hand off to carrier B that directs the call towards carrier C

Either way, depending how and where the call happens, it's entirely possible some go through a more TDM backbone or a more SIP one and those different paths are showing either an e164 numbering format or not.